1. Field of the Invention
The present invention relates to a process for preparing highly absorbent powders of alkali metal silicates. More specifically, the present invention relates to a process for spray drying sodium or potassium silicate solution to prepare highly absorbent powders of sodium or potassium silicate with an unusually high degree of internal porosity.
2. Prior Art
Primarily because of environmental concerns, phosphates are considered an undesirable component of household detergents as substitute water-soluble sodium silicate powders have been added to perform some of the dirt-suspending and deflocculating functions of the phosphates and provide the necessary alkainity for a satisfactory cleaning operation. Enhanced cleaning has also been sought by increasing the concentration of ionic surfactants such as sodium salts of linear alkyl-aryl sulfonates and nonionic surfactants. The latter are more desirable because they do not generate the "curds" (soap) of hardness ions in water in the absence of an effective sequestering agent such as phosphate. Problems have been encountered in using these modified formulations because of the increase in the amounts of the low melting, relatively soft sodium alkyl-aryl sulfonates and the substantial increase in the amount of liquid nonionic materials. This has led to soft, sticky detergent powders which do not flow well and which cake badly in the box on storage.
It is therefore imperative that a highly absorbent material be provided which is suitable in both an ecological sense and in a commercial sense, the latter being as a constituent of detergent formulations which can serve as a carrier to absorb large amounts of nonionic detergents. Such a material is disclosed in U.S. Pat. No. 3,839,226 and copending application Ser. No. 472,094, filed May 22, 1974, now U.S. Pat. No. 3,932,140. However, the processes disclosed therein require a multiplicity of steps and larger equipment investment. Thus, there is a need for a desirable process for preparing commercial quantities of silicate powders having improved absorbency.